The equation of a standing wave is represented as follows:
- y = y0sin(kx -
t) + y0sin(kx +
t)
Using a trigonometric identity to simplify,
- y = 2y0cos(
t)sin(kx)
where y
0 is the amplitude of the wave,

is 2

times the frequency (in Hz), k is 2

divided by the wavelength (in meters), and x and t are variables for longitudinal position and time, respectively.
Now here given equation is
y=acoskx coswt
so velocity = v = w/k
Now find expression for space density